This invention relates to a friction joint and to hardware incorporating same.
In building hardware items such as a handle for latching closed a closure, eg a window, it is known to provide some degree of resistance to movement of the handle. This enables the handle to remain, say, in a non-latched position. Without the resistance to movement the handle would tend to fall back to its latched position which is inconvenient to the user who needs to revert the handle to the unlatched position so as to move the closure to a closed position. The handle can also cause damage to surrounding frame, seals and the like in the event that the closure is moved to the closed position without the handle being held in or prior moved to the non-latching position.
This resistance to movement can be achieved by torquing down a threaded element so as to cause some frictional contact between a moving portion of the fastener and some static portion (usually the mounting base of the fastener). A problem with this approach, however, is to achieve uniformity of frictional contact from one handle to the next. For example, while the threaded fastener can be tightened to the same torque level, this predetermined torque level can be achieved because of contact between elements within the pivot joint which, nevertheless, very quickly wear or xe2x80x9csettlexe2x80x9d thereby resulting in the joint becoming loose. This problem can also arise when the level of frictional contact is achieved by swaging or otherwise deforming the end of a rivet means which is used to combine the joint components together.
Furthermore, variation of friction also occurs over time due to wearing of the contacting components.
The variation that occurs when tightening a rotating assembly to a torque is caused by the fitment of the threaded fastener to its threaded bore. Put simply, the tighter the thread, the less axial load imparted onto the rotating assembly for a given torque.
This common xe2x80x9ctorque methodxe2x80x9d is also sensitive to the degree of accuracy that the fastener can be tightened to. For example, when using a pneumatic screwdriver fitted with a spring loaded clutch and common self tapping screws, there is significant variation in the actual tightness from one assembly to the next.
An object of the present invention is therefore to provide an improved friction joint whereby a desired friction level is achieved as a consequence of assembly of elements included in the joint.
In the context of the present invention and the following disclosure the reference to friction is intended to mean that there is a restriction to movement between at least a movable element and a non-movable element such that the friction joint can enable relative movement between the parts to be prevented unless a moving influence is applied.
The friction joint according to the present invention has particular application to a fastener which is useable to latch in a closed position a sliding sash of a window relative to another sliding sash (in a double hung arrangement) or relative to a window frame. However, the friction joint is not limited solely to this application and can be used in connection with latches for latching any closure in a closed position relative to a fixed frame or some other movable element. Thus, the item of hardware can be used for latching a sliding door with a frame or to another door (preferably sliding) member.
Broadly, according to one aspect of the present invention, there is provided a friction joint coupling together first and second elements such that relative rotational movement therebetween can occur, such fastening being achieved by a headed fastening means located through an opening in the second element and engaged with the first element, the head of the fastener means being engageable with an end of a sleeve of the second element, said sleeve being compressible upon an axial tightening movement of the fastening means applying a force to said end of the sleeve.
Preferably a washer means is located between the head of the fastener and the end of the sleeve.
According to a second broad aspect of the invention there is provided a fastener incorporating the friction joint of the first broad aspect including a wedge element mounted for rectilinear movement in a direction substantially transverse to the axis of rotational movement of the friction joint and drive means coupling the wedge element with the second element such that rotation of the second element is translated into said rectilinear movement of the wedge element.
Preferably the fastener includes a bracket with which the wedge element is engageable. The bracket can have a hook shaped projection and the wedge element an inclined portion which is engageable with the hook shaped projection.
In the preferred form an operating lever is coupled to the second element. Preferably the lever is releasably coupled to the second element.
According to one form of the invention there is provided locking means for locking the lever in a position corresponding to the wedge element being engaged with the bracket. The locking means can be mounted by a face plate through which the lever extends to engage with the second element.
Preferably the wedge element is slidingly engaged in a channel formed with the first element. The first element is in one preferred form provided with means for fastening to a fixture.